1. Field of the Invention
The present invention relates to a variable valve mechanism used for a valve system or the like of an engine, for example, and particularly relates to a cam-switching variable valve mechanism configured to select any one of a plurality of cams by sliding a cam unit in an axial direction (a cam axial direction), the cam unit being provided around a camshaft.
2. Description of Related Art
Conventionally, as a variable valve mechanism that can change a lift characteristic of an intake valve or an exhaust valve of an engine, a Variable Valve Timing (VVT) that can continuously change a valve timing is used widely. Further, as described in Published Japanese Patent Translation of PCT application No. 2010-520395 (JP 2010-520395 A), for example, there has been publicly known a cam-switching variable valve mechanism configured such that a cam carrier (a cam unit) including a plurality of cams is provided around a camshaft, and any one of the cams is selected by sliding the cam carrier in an axial direction of the camshaft.
The variable valve mechanism of the conventional example is provided in a multi-cylinder engine in which two intake valves and two exhaust valves are provided for each cylinder. In a cam carrier provided for each cylinder around an intake camshaft, three cams, i.e., a large cam, an intermediate cam, and a small cam are provided for each of the two intake valves. The cam carrier is slid in a cam axial direction so as to switch among a low lift position at which the small cam is selected, an intermediate lift position at which the intermediate cam is selected, and a high lift position at which the large cam is selected.